1. Field of the Invention
The present invention relates to enclosures and, more particularly, to insulated closure structures for walk-in enclosures such as refrigerators and freezers.
2. Description of Related Art
Walk-in freezer or refrigerator units are large, enclosed spaces used for the storage of perishable items. In many situations, pallet jacks or other means of transporting pallets of stored goods are used to put in or remove the goods from the freezer or refrigerator units. In these situations, it is necessary to have a threshold flush with the inner and outer floors. The standard doors built into the freezer or refrigerator units are too small to allow easy maneuvering of the pallet jacks, with the result that the doors and frames are easily damaged and often require replacement. Typical replacement closures known in the art are units that are affixed externally to the outer wall. These units protrude into the workspace, are weak in respect to thermal barrier properties, and are easily damaged.
The replacement enclosures must perform the same functions as the original closures. They must maintain the temperature differential between the inside of the freezer or refrigerator unit and the outside. The closure should not allow moisture condensation to form on the exterior. The threshold of the closure must remain free of ice to prevent hazardous footing conditions. The replacement closure must be sufficiently insulated and sealed at all points to prevent thermal leakage into the walls or around the door.
In use currently known closure structures are frequently damaged by impact from pallet jacks when operated carelessly inside the enclosure. As enclosure doors are typically made of a pair of spaced-apart, fairly thin metal sheets having a foamlike insulating material disposed between the sheets, an object such as a lifting device hitting the door can cause serious damage and require expensive repairs or complete replacement.